1. Field of the Invention
The present invention relates to a system of determining a data delay margin in electronic equipment operating in synchronization with a system clock (machine clock), and more specifically to a marginless status determination circuit for determining a marginless status for a case in which a data delay margin is reduced corresponding to, for example, a change in temperature.
1. Description of the Related Art
Generally, the operation of electronic equipment such as a microcomputer, etc. is subject to environment conditions, for example, a change in temperature, etc., the operation margin decreases as the temperature rises, and in the most extreme case an error such as a malfunction, run away, etc. occurs.
Therefore, generally in designing electronic equipment, the worst value is assumed as an environment condition for using the electronic equipment, and a timing margin is assigned to perform a normal operation even under the worst condition. In this case, it is necessary to set in advance a temperature at which a marginless status is assumed to occur. Since the severest condition in the environment conditions of shipping a product, for example, the severe ambient temperature is set, a margin normally remains at the actually applied temperature. That is, the overly severe condition is set.
Described below is a document of the prior art which introduces a conventional technology for guaranteeing both performance and reliability of electronic equipment in response to a change in the above-mentioned ambient temperature.
The patent document 1 described below discloses the technology of electronic equipment operating in synchronization with a system clock switching the frequency of a system clock by selecting any of a plurality of clock signals having different frequencies depending on the detection result of an ambient temperature.
However, in the patent document 1, a clock frequency is switched when an ambient temperature reaches a predetermined temperature. Therefore, the problem that it is difficult to set a switching temperature cannot be solved. Furthermore, since a temperature sensor and an A/D converter for conversion of a detected temperature to digital data are required, the area of a circuit undesirably increases.
[Patent Document 1] Japanese Published Patent Application No. Hei 3-251912 “Electronic Equipment Having Function Of Switching System Clock”